Approaching a traffic signal, you’ve no doubt found yourself in what’s called the “dilemma zone”: It’s changing to yellow; what’s the safest course of action? Should you slow or should you go?
With signal phase and timing – aka SPaT – you go beyond making a decision based solely on the current color of the light. The signal can broadcast data about when the light will change and your vehicle can interpret that data to tell you where you are in relation to it.
A new signal pilot project on Mission Street in Salem is sharing that data in a new way – via the internet – and laying the groundwork for that information to eventually be broadcast directly to your vehicle. This summer, seven Advanced Transportation Controllers (ATCs) were installed along the corridor between 17th Street and I-5 on Mission.
“The concept of this connected vehicle pilot is that we’ll be able to get information from the infrastructure to vehicles to help drivers make more informed decisions,” says Julie Kentosh, Statewide Traffic Operations Engineer at ODOT. “We envision that this data would be integrated into an on-vehicle dashboard.”
“In the future, we hope it will have capabilities to warn of pedestrians, emergency vehicles and more,” Kentosh says.
Convenience and safety
For testing purposes in this proof-of-concept project, ODOT is using a smartphone application that can tell a passenger in the car how much time is left on the green light, how long it is until the light turns green or even the most efficient speed to hit all seven lights in the corridor on green. This test app is not meant for public use. The intent of this project is to make the data available to third-party developers to potentially develop apps that use the data in creative, interesting and useful ways and get the information directly to the vehicle.
Beyond convenience, the project also offers safety benefits. Studies have shown that the countdown pedestrian lights, ostensibly for walkers, also show a decrease in vehicle crashes because drivers use the information to make more informed decisions in the dilemma zone.
While it hasn’t been quantified yet, Kentosh says, they’re hopeful that the more personalized, up-to-the-second data in this project could help drivers make even safer decisions.
The new signal controllers also allow staff to monitor signals remotely.
“We can pull up this remote interface, and we can find out at any time if a signal’s working properly, if it’s in flash, if it’s running yellow, green or red,” Kentosh says. “This allows us to proactively manage our signals rather than reactively waiting for a complaint from the public.”
About the technology
This pilot is unique because it’s using the internet exclusively to share both SPaT (signal phasing and timing) and map data. SPaT data includes time to green light, time remaining on green and so forth. Map data uses a geographic information system (GIS) to determine what lane the vehicle is in and whether it is turning left, right, or passing through the intersection – that way the system can provide SPaT data specific to that movement.
“The sharing of SPaT data itself is not new,” says Galen McGill, ITS manager at ODOT. “The innovation in this project is building the map data in the central signal system and publishing it along with the signal phase and timing data via the internet.”
Publishing the two types of data together from the central signal system helps prevent the map and signal data from getting out of sync as updates are made to intersection or timing plans. It also gives developers everything they need to utilize the data. Past projects required gathering and providing intersection plans and timing sheets to allow developers to make use of the SPaT data.
While there is growing support in the auto industry for vehicle-to-vehicle and vehicle-to-infrastructure communication using a specific radio frequency known as DSRC, or Dedicated Short Range Communications, there are many more cars on the road today with internet connectivity. ODOT plans to support both methods for communicating with connected vehicles.
“This pilot is setting up infrastructure that lets us share data through the internet and DSRC at roadside,” McGill says. “No matter what the future connected vehicle environment is, we’ll have systems in place.”
ODOT plans to do additional pilot projects next year utilizing DSRC radios for publishing SPaT and map data from the roadside.
This pilot project is helping ODOT prepare for and support the needs of connected and automated vehicles, and in the process, helping make the dilemma zone less of a dilemma.